UCC24612: About delay in turn-off

user1590158

Part Number: UCC24612

The UCC24612-1 is used in the QR flyback circuit.
I have a question regarding the delay in turn-off of UCC24612-1.

Is there anything I can try on this issue?

It is irregular and not load dependent.
Some ICs do not occur even in the same reel lot.

Changing to a FET with a large RDS_ON will improve it, but it cannot be suppressed.
The point at which Vgs drops (VTHREG) also appears to change.

over 3 years ago

0 Mike O' over 3 years ago

TI__Guru 66135 points

Hello,

Could you share a schematic of this design?

Regards,

0 user1590158 over 3 years ago in reply to Mike O'

Prodigy 80 points

Hello Mike,
Thank you for your reply.

I will send you the schematic and PCB artwork.
The previous waveform is THP4R40ANL.
Changing to THP8R80ANH improves it, but does not completely suppress it.

Best regards,

0 Mike O' over 3 years ago in reply to user1590158

TI__Guru 66135 points

Hello,

I reviewed your schematic and don't see an issue. The SR is supposed to turn on when than there is zero current going through it. It seems delayed. Do you have any capacitance on the VD pin of the UCC24612? If you did that would cause a delay that would cause the behavior that you are seeing.

I will review that artwork and schematic after you send it when I have a chance.

Regards,

Power management

Power management forum

UCC24612: About delay in turn-off